The complexity of structures, for example, used in oil and gas subsea exploration is increasing to satisfy the many requirements in terms of thermal behavior, geometry, multiple fluid flows, flexibility and mechanical characteristics. For example, some umbilicals or risers can be used to connect wells or facilities at the sea bed to, for example, floating facilities at the sea surface. Further examples of such structures include manifolds, separators and control units. It is desirable to monitor such connections in order to prevent structural failure due to fatigue, corrosion, erosion or blockage, which can be caused by the deposition of parts of the flow components (e.g., such as wax, hydrates, scales, asphaltenes, etc.).
Damage to such structures also can be due to human activity, such as fishing or laying and removal of anchors. Damage can also be the result of excessive stresses or shocks during transportation or deployment. Manufacturing defects can also compromise the quality of such structures.
For such reasons, leaks can develop in localized parts of such structures. Often such a leak is detected after it has become large, leading to unplanned repairs that can take a long time, as equipment, material and personnel need to be mobilized on short notice. Locating the leak is also an important issue. Sometimes the leak cannot be located with a simple visual inspection, requiring the replacement of long sections of the structure. For example, leaks can be of seawater into the structure, which can promote problems, such as corrosion or contamination of hydraulic lines, or leakage of oil or gas out of the structure.